CSI-RS Subframe Allocation for CoMP Power Saving
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Solution Overview
Problem
In LTE-A systems, the transmission of CSI-RS for CoMP is affected by the power saving effect when using Fake MBSFN subframes, leading to reduced power efficiency due to the need for CSI-RS transmission in subframes where only the head CRS is transmitted.
Innovation Solution
A wireless communication device and method that disposes and transmits CSI-RS in subframes excluding those incapable of transmitting the signal and other than MBSFN subframes, allowing for orthogonality and multiplexing without compromising power saving effects, by using subframes #4 and #9 for CSI-RS transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CSI-RS is transmitted in Fake MBSFN subframes to enable CoMP, then channel state information estimation is improved, but power saving effect is reduced
Solution Approach 1:
The patent segments the subframe structure by identifying specific subframes (#4 and #9) within a frame for CSI-RS transmission. This segmentation allows the system to transmit reference signals only in selected subframes rather than all subframes, thereby maintaining power saving effects while enabling CoMP functionality.
Solution Approach 2:
The patent implements periodic transmission of CSI-RS in specific subframes (#4 and #9) rather than continuous transmission. This periodic action pattern allows the base station to transmit reference signals at regular intervals, reducing overall power consumption while maintaining adequate channel state information estimation capability for CoMP.
2Use of energy by moving object
If CSI-RS is transmitted in subframes #4 and #9 to maintain power saving, then power efficiency is improved, but orthogonality between close cells may be compromised
Solution Approach 1:
The patent applies local quality by configuring different CSI-RS transmission patterns for different cell groups. Close cells (first cell group) and distant cells (second cell group) can use different subframe configurations or resource element allocations within subframes #4 and #9, allowing orthogonality to be maintained locally for interfering cells while still using the power-efficient subframe selection.
Solution Approach 2:
The patent resolves the orthogonality issue by moving to another dimension - using frequency domain resource element allocation within the selected subframes. By allocating different resource elements (subcarriers) to different cells within subframes #4 and #9, the system maintains orthogonality between close cells while preserving the power saving benefits of selective subframe transmission.
Data Source
AI summary
The transmission of a reference signal, such as a CSI-RS, is enabled while maintaining a power saving effect when performing inter-cell cooperative transmission/reception or the like in a plurality of cells. In order to realize inter-cell cooperative transmission/reception, a CSI-RS which is used for estimating the state of a spatial propagation path of a communication line is generated by a CSI-RS generation unit, and the CSI-RS is disposed in a predetermined subframe by a disposition unit and transmitted. At this time, when a frame has ten subframes #0 to #9, the CSI-RS is disposed in the subframes #4 and #9, which are subframes excluding the subframes #0 and #5 incapable of transmitting a CSI-RS and are subframes other than subframes capable of acting as MBSFN subframes when discontinuous communication (Extended Cell DTX) is performed so as to achieve power saving, and transmitted.